In our SharePoint 2010 environment, Search service application is not crawling for a site collection alone and it crawls for the other sitecollections are in the same contentDB.
Have verified the site collection search settings and found those are fine.
Verified in the crawl log and found that it throws “337” error while crawling the site collection and stopped.
I guess, 337 refers to "The server is unavailable and could not be accessed. The server is probably disconnected from the network."